Polygonal cutting insert

Abstract

A polygonal indexable cutting insert for cutting aluminum metal comprises rounded cutting corners with adjacent side surfaces joined at an angle of from about 33 to about 35 degress. Grooved recesses extending along each cutting edge have a particular geometry which includes a shallow descending surface followed by a steeply descending surface leading to the bottom of the grooved recess. An ascending surface directs the chip upwardly toward the top face and away from the insert and the cutting edge.

We claim: 
     
       1. A polygonal indexable cutting insert comprising a top face forming a central island and a bottom face, said faces being substantially parallel, four peripheral straight side surfaces having a clearance angle of from about 82 to about 88 degrees with respect to said top face,   said peripheral side surfaces forming a pair of adjacent side surfaces and a pair of opposite side surfaces, said opposite side surfaces being substantially parallel and said adjacent side surfaces merging at an angle of from about 32 to about 38 degrees,   a pair of rounded cutting corners having a radius of from about 0.3 to about 0.6 inches and being formed at the juncture of said adjacent side surfaces,   a pair of cutting edges being substantially positioned in or immediately below the plane of said top face and having straight portions extending away from each corner and,   grooved recesses extending rearwardly from said cutting edges a distance of from about 0.04 to about 0.06 inches and merging at said corners to from a chip breaker, each of said grooves recesses terminating at said central island at a distance spaced from said remaining grooved recesses   each of said grooved recesses comprising a descending surface of uniform width extending downwardly from a respective cutting edge, and an ascending surface extending upwardly from said descending surface to said central island, said ascending surface is at an angle of from about 16 to about 20 degrees with respect to said top face,   said descending surface comprises a first surface of uniform width directly adjoining said cutting edge and a second surface of uniform width joining said first surface to said ascending surface, said first surface is at an angle of from about 4 to about 6 degrees with respect to said top face and said second surface is at an angle of from about 17 to about 23 degrees with respect to said top face,   said respective first and second surfaces being uniformly spaced from and extending entirely around a respective rounded corner and said ascending surface forming a rounded contour at the juncture with said central island for providing enhanced chip flow.   
     
     
       2. A polygonal indexable cutting insert according to claim 1 wherein said clearance angle is about 85 degrees. 
     
     
       3. A polygonal indexable cutting insert according to claim 1 wherein said cutting edges lie below the plane of said top face. 
     
     
       4. A polygonal indexable cutting insert according to claim 3 wherein said insert comprises a centrally located opening extending entirely through said insert from said top face to said bottom face. 
     
     
       5. A polygonal indexable cutting insert according to claim 4 wherein said opening bevels outwardly at the junction with the top face. 
     
     
       6. A polygonal indexable cutting insert according to claim 5 wherein each rounded cutting corner has a radius of from about 0.4 to about 0.5 inch. 
     
     
       7. A polygonal indexable cutting insert according to claim 6 wherein said ascending surface is at an angle of 18 degrees.